I have a Bambu X1 Carbon with AMS and I print ASA and ABS functional parts without too much trouble.
I have a new requirement that calls for the part to be small, thin and slightly flexible. When I try to produce this part in ASA or ABS, the part is too brittle and breaks after a little flexing. I’ve read that PA (aka “Nylon”) is more durable than ABS/ASA because it is more flexible. I would like to try PA or one of the PA copolymer blends.
I have printed using Bambu’s PACF before and with the chopped carbon fiber, the result is too rough for small parts. So, I’m looking for a PA (Nylon) without any carbon or glass fiber added - preferably something that prints like ASA/ABS.
I am well aware of TPU and use that regularly, but TPU is too flexible for this application. I don’t need a “live hinge”. I do need something that can flex 5-10 degrees at least a couple of times.
Do any of you have experience printing non-filled PA filament on the X1C? Do you have any recommendations on brands, specific products and X1C settings?
Can you define what is “small, thin and slightly flexible”. I ask because often we see questions where the objective exceeds the resolution of the technology. So if you’re let’s say expecting to print a let’s say a musical reed 12x67x0.5mm and expected it to let’s say have the strength of a let’s say a bamboo reed, I’m afraid you would be asking too much of the technology. Likewise, how flexible must it be? Flexible like spring steel or flexible like a similar sized piece of wood.
Either way, ultimately I’m afraid only you can judge the suitability of the material for your specific application but I’m sure there are enough people here with experience that can provide an educated guess if you can provide more data.
Thanks for your reply. I agree that this application is approaching the limits of FDM technology. However, I’ve already printed dozens of these parts and have placed them in service, so I already know that both design and production are viable.
To give you a better idea, the part is a “blind retainer” meant to fasten objects to a 20-gauge sheet metal panel populated with 6.35mm holes. The panel is 1.2mm thick and there is no access to the back side of the panel - everything must be inserted and tightened from the front.
I have designed and produced 6.20mm sleeve anchors which fit into the hole. Each sleeve is 7.5mm long and divided laterally into four “leaves”. There is a conical wedge with a M2 heat-set insert that is pulled into the sleeve by an M2 screw from the front of the panel. When the screw is tightened, the wedge in drawn in, causing the leaves to expand and thereby fixing the retainer. Only about 1.5mm of the sleeve protrudes behind the panel.
The problem is the parts are fragile and so some break if not inserted gently. Others break when the part is tightened and the “leaves” flex, even though they flex only a few degrees.
This part works using ABS/ASA. I’m thinking it will work better and be more durable using PA. If Bambu sold non-filled PA, I would start with that. Since Bambu doesn’t offer any filament like that, I’ll have to start with something else. That’s why I’m looking for recommendations.
Sounds a lot like a wall toggle. You might consider PA-12 or PA-11 (Nylon) filaments. They offer strength as well as flexibility. The PA-6 and PA-66 Nylons are somewhat stiff and often used to replace metal parts. The prime consideration for printing will be the temperature required to print these filaments and the need to keep the filaments bone-dry (< 1% water). They all pretty much require oven drying before use and need to be kept in a sealed container with desiccant.
And another thing, you will want a well-ventilated area and perhaps a breathing mask if you intend to watch the prints.
I’m struggling to visualize your part but I’ll try. A picture would help.
You mention that you are using heat-set threads. Have you tried out PC filament? Whereas PC filament will work well with heat-set, have you tried PC with plain holes and then tapping the threads after the print? I ask because, in my experience, PC makes a very good stiff machinable part that lends itself to cutting. My thinking is that PA is just going to be too soft for your application, and I understand why CF may be too abrasive. PC might be in your desired goldilocks zone. The key here is that it may not make the prettiest parts and you will want to calibrate the filament for optimal precision. My experience with PC is that the defaults profiles are too inaccurate. Also note that PC requires 100c bed temp and high nozzle temp. However, I have made some very durable parts with PC and cut my own threads for use with metal screws and bolts.
I should also add, rather than use 100% infil, if you use high wall count so that you get 100% contact, it will make for an extremely stiff and strong product.
The conical wedge is the only part with a heat set and that part works perfectly well.
The problem is the body (consisting of retainer head and sleeve). Since the sleeve is already 6.20mm before expansion, the leaves do not have to move far to fill-up the 6.35mm hole. But that 5 degrees they need to flex causes them to sometimes break.
When they break, it is nowhere near the steel or hole - they either break where they connect to the head or more typically, about halfway down the sleeve. The ABS/ASA is simply too brittle.
That’s why I was looking for a material that is a little more flexible - something that can flex 5 degrees several times and survive.
That’s a great thought about the PC that I had not considered. I have some PC in inventory. I’ll give that a try and post back here with the results.
Thanks for the good info. I was aware of how hygroscopic PA is and that it is frequently necessary to dry even brand-new, sealed rolls. In light of that, I was already planning to dry the material for a day or so before printing.
I was not aware of the differences between PA-6, PA-66, PA-11, etc., but I’ll follow your rec and try to obtain one of the softer flavors.
Before experimenting with different materials, try using any available material and avoid brass inserts. While brass is strong, it sacrifices plastic wall thickness. Instead, include a small hole in your model for direct tapping. The combined strength of thicker walls and the ability to make disposable components might make a plastic part more practical than a metal/plastic combo.
Once you’ve experimented with tapping the holes directly, you’ll have a better feel for how the product will perform. For me as an example, I do all my prototyping in PLA. Then I move up to PETG and for the most strongest I use PC. Truth be told, I have PLA parts using metal screws that were tapped just using the screw itself as a tap and the performance will surprise you.
I’m sure in your line of work you have ample access to taps, but this lazy man’s drill-tap combo that I purchased some time ago is this one from Amazon is my go-to tool of choice when making cutting threads directly into plastic. I keep it right by my other 3D printing tools. I have another one for Metric. What I like is the combo drill bit, which allows me to be lazy about dimensioning holes in CAD.
Interesting thread… Isn’t PP one of the best for flexing many times? But it’s a pain to print IIRC. Maybe some co-polymer is more fun?
But it seems to me that between PA12 and PC you should get to something that works.
Another thought is that by reducing infill where the ASA part tends to break you may be able to let it flex without cracking. If that’s not right where it could get crushed by the hole into which it’s inserted the reduced infill would not detract from the pull-out strength of the whole assembly.
Yet another thought: I assume the cracking happens along layer lines as I assume you print the little piece standing up. To increase layer adhesion increase temperature, reduce speed, slow the fan. I really like Polymaker ASA and have recently cursed a roll of 3DXTech ASA which had horrible layer adhesion in comparison, so trying a different ASA (or ABS) may be the ticket…
PC will be worse, it feels quite stiff and brittle to me. It has a tendency to fail by shattering…
I’d have thought pretty much any nylon should be fine (perfect, even, because of the flex and high toughness). Or consider PETG if you can get away with it which should have more flex than ABS (and is incredibly cheap).
If you really want to live on the bleeding edge, there exists stuff called “rigid TPU” which is TPU but with a very high shore hardness. I’ve used the “Armadillo” brand made by Ninjatek.
Yes, this little project has been interesting because the problem is part kinematics and part material sciences.
I don’t need the part to flex many times. If it can flex for five cycles and survive, I would consider that a win. From the materials science perspective, that’s why I wanted to try PA12\Nylon.
Olias makes a great point about threading PC and skipping the heat insert. That would allow me to make the cone wedge smaller, which would allow the leaves to be made thicker. I’m going to give that a try.
The breaks almost always occur about halfway down the length of the sleeve - not at the very end which is the area under the greatest stress. I think that is because as the end opens like a daisy, those leaves in the middle bow in towards the screw.
It’s possible the middle of the sleeves is moving a lot further than the extreme end. I intend to test that theory by making a few test pieces where the center of the sleeve is solid and not hollow. I think the best approach for that is to create a cylindrical spacer that slips over the screw and occupies the hollow space between leaves and screw. If the space is occupied, the leaves can’t bow in as much.
This has become quite a science project.
Thanks to everyone contributing ideas and suggestions!
UPDATE: I eventually found a solution to this project and I wanted to let anyone interested know what I learned.
I followed Olias’ suggestion and ordered PC filament and tools to drill and tap M4 holes. I bought an Accusize 0001-0052 Metric Tap & Drill Set, which is really high-quality and surprisingly inexpensive - I recommend that set for anyone who needs to machine plastic and soft metals. I also bought Bambu PC filament, which is already profiled in the slicer and so it was plug-and-play - no experimenting.
The PC prints very well on the high-temperature plate with glue stick and the result is hard and solid. This is my first time working with polycarbonate and I found it very easy to use. It prints hot, but does not shrink nearly as much as ABS/ASA. I didn’t have any bed adhesion or warping issues. Machining the finished PC part is almost like machining aluminum. PC feels almost like a ceramic rather than a plastic.
I changed the design so there is an “adapter” that interfaces between the metal panel with holes and whatever it is I’m trying to mount. The adapter has the expanding petals on one side to engage with the holes in the metal plate. The other side has heat press inserts for M4 screws and is tapped for M4 grub screws. As the grub screws are tightened, they expands the petals to engage the holes in the metal panel. It works well enough that when tightened, it can’t be pulled off the metal plate without damaging the plate. It’s absolutely rock-solid.
This solution achieved most of my goals. I don’t know if the PC parts will be reusable if removed, but that has become a lesser concern. Thanks to everyone for the comments and suggestions!
Accusize Metric Drill and Tap Set (just the smaller bits and taps):
Hi.
I test eSun PA-CF, Overture easy nylon and Taulman bridge 230.
Overture EA it’s brittle and very difficult to print, it’s more similar to abs that Nylon.
At the end I can get really good results with the Taulman one, the big problem
of the Taulman is warping, really very high, I learn thar tree supports and slim parts work better with it.
The Taulman is really very flexible with incredible layer adhesion, I’m looking
for another nylon minus prone to warping and stiffer, thats becasus I test the
overture, but It isnt a good option
Any other PA recommended?
You might consider PA-12 or PA-11 (Nylon) filaments. They offer strength as well as flexibility. The PA-6 and PA-66 Nylons are somewhat stiff and often used to replace metal parts. The prime consideration for printing will be the temperature required to print these filaments and the need to keep the filaments bone-dry (< 1% water). They all pretty much require oven drying before use and need to be kept in a sealed container with desiccant.
